Astrospheres
The heliosphere simulation code is also applied to other cool stars (similar to the Sun, but also cooler stars like K and M dwarfs) interacting with their neighboring interstellar gas, giving rise to astrospheres. Astrospheres of nearby stars can be detected by an extra absorption component in the stellar light (in stellar Lyman-alpha profiles) due to the star's hydrogen wall, the latter being a direct consequence of the interaction of the stellar wind with the ISM. This absorption component has been detected in two dozen high-resolution UV spectra obtained by the Hubble Space Telescope.
The physics of neutral/plasma interaction applies to other suitable astrophysical winds as well, such as winds from red giants (they are massive, and mostly neutral), and also three wind configurations like alpha Cen (two stellar winds of a close binary pair, together with the interstellar wind).
General Structure
The Bow Shock is the line where the interstellar plasma is decelerated from supersonic to subsonic velocities. The supersonic stellar wind terminates at the Termination Shock where it becomes subsonic, shock-heated, and starts flowing tailward to the astrotail. A contact discontinuity, the Astropause, separates stellar wind plasma and interstellar plasma.
The interaction of the protons of the plasma
with neutral hydrogen, to leading order, is charge exchange whereby the
neutral atom loses its electron to the proton, making the latter a
newly born
neutral hydrogen atom. Charge exchange
decelerates the neutrals, filters the incoming neutrals,
and creates a hydrogen wall, an accumulation of neutral hydrogen (lower
panel) that also is heated and decelerated as compared to the ISM.
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